The present invention relates to hand-held apparatus for propelling light watercraft, such as paddles for moving canoes through water.
Conventional canoe paddles include a straight shaft having typically a "T"-shaped hand grip at the top end of the shaft, and a blade secured to a lower end of the shaft, wherein an elongate grip portion of the "T"-shaped hand grip extends in both perpendicular alignment with the shaft, and in parallel alignment with a plane defined by a flat surface of the blade, meaning a surface of the blade extending between side edges of the blade. It is well known that in use of such a conventional paddle to propel a canoe through water by a single user, the user kneels or sits in a rear or stern section of the canoe and places the blade of the paddle into the water so that the flat surface of the blade is perpendicular to a desired or forward direction of travel. The user holds the "T"-shaped hand grip of the paddle in one hand, and a lower-mid section of the shaft in the other hand. For example, if the user places the paddle on a right side of the canoe looking forward from the stern (e.g., the starboard side), the left hand of the user will be on the hand grip of the shaft, and the right hand will be on the lower-mid section of the shaft. The user then pulls the paddle toward the rear of the canoe through a stroke, causing the canoe to move forward in a conventional manner. When the user's arms can reach no further backward, the paddle is removed from the water, brought forward again, placed in the water for another stroke.
Because such strokes of a conventional canoe paddle are not aligned with a center of drag of the canoe, the canoe tends to turn in a direction that is opposite the side beyond which the paddle is stroked. If the paddle is moved through a stroke on the starboard side, the canoe will turn to the opposite, or port side. One common approach to counter that non-linear thrust characteristic of conventional straight canoe paddles is to frequently switch the paddle from the starboard to port side of the canoe after several strokes, and back and forth in a repetitious manner to move the canoe in a twisting, yet overall straight direction. Another and perhaps more common approach is the well-known "J-stroke". In executing a J-stroke, as shown in FIG. 5, as the paddle nears the end of the stroke wherein the user's arms can reach no further toward the stern of the canoe, the user rotates the paddle so that the flat surface of the blade, while still underwater, is aligned parallel to the direction of travel of the canoe. The user then pushes the blade away from the canoe before the blade is extracted from the water, thereby generating a counter turning force to the non-linear thrust of the conventional straight shaft canoe paddle.
While either switching from side-to-side or use of a J-stroke effectively moves the canoe in a straight direction, both techniques have substantial disadvantages. Switching from side-to-side requires additional energy, typically causes water to drip into the canoe as the paddle passes over the canoe, and enhances a risk of dropping the paddle. Use of the J-stroke also requires use of energy of the user in pushing the paddle blade away transverse to the direction of travel of the canoe, which causes a slight drag effect, slowing the canoe. Even worse, the J-stroke requires twisting of the user's wrists, and application of force through the wrists when twisted. Such repeated, stressful stretching of the wrists gives rise to a risk of repetitive motion trauma. Additionally, the outward movement of the user's arm away from the canoe is an awkward and therefore tiring motion.
An additional drawback of conventional straight shaft canoe paddles is an inefficient use of the paddle through a full length of a stroke from paddle insertion into the water to paddle extraction. Because the shaft is straight, the ability of the user to extend the blade forward, beyond the knees of a seated user, is limited by flexibility of the user's wrist on the arm grabbing the lower-mid shaft. As seen in FIG. 7, the blade cannot extend much further than the user's knees because of limitations in flexing the wrist of the user's pulling arm toward the user's shoulder. Consequently, the blade of the conventional paddle enters the water at a near vertical position relative to a surface of the water, and leaves the water at a position wherein the blade is almost parallel with the surface of the water. Therefore, the flat surface of the blade is roughly perpendicular to the direction of travel and the surface of the water for only a small portion of the full length of the paddle stroke from paddle insertion to extraction. For a substantial portion of the length of the stroke, the flat surface is moving to become parallel to the surface of the water, so that the user is expending energy to pull the paddle up toward the surface, rather than backward, to move the canoe forward.
Additionally, a portion of the full length of the paddle stroke wherein the user can most efficiently exert force on the paddle to move the blade toward the rear of the canoe is also only a small portion of the full length of the paddle stroke. In other words, while the user's arms are extended well in front of the user's shoulders, the user can exert substantially more force on the paddle than when the user's arms are closed into and near the user's chest and shoulders. However, as seen in FIG. 7, the blade of a conventional paddle is efficiently disposed in the water for only a small portion of the full length of the paddle stroke while the user's arms are forward of the user's shoulders. Therefore, conventional straight shaft paddles are inherently unable to take efficient advantage of a full length of a paddle stroke. If a second user in a front or bow of the canoe is simultaneously using a paddle on the opposite side of the canoe, some of the offset thrust of the stern user is compensated for, but the stern user must still use the J-stroke or other means to maintain straight travel.
Many solutions have been developed to resolve the conventional straight shaft paddle problems of both inefficient blade positioning through a full stroke length and also the non-linear thrust characteristics of such paddles. No paddle designed to solve both of those problems has to date become popular or widely used. A variety of bent shaft paddles are known that enable a user to place the blade in the water further forward of the user's knees, and some of these result in a more efficient use of the blade through the full length of the stroke. However, such bent shaft paddles give rise to a variety of problems related to the bent shaft. For example, in "back-paddling", for control of a canoe during steering, accurate positioning, docking, or landing, etc., use of bent shaft paddles results in substantial torsional or twisting loads on the shaft, which must be controlled by the user's wrists. Such torsional loads are difficult in flat water canoeing, and may be crucial in white water canoeing. Additionally, bent shaft paddles are also susceptible to greater torsion loads upon extraction and insertion of the paddle blade into the water than are straight shaft paddles, which loads must be compensated for by the user's wrists. Such bent shaft paddles do not change the non-linear thrust characteristics of conventional paddles.
One solution to the non-linear thrust characteristics of canoe paddles is shown in U.S. Pat. No. 3,970,032 issued on Jul. 20, 1976 to Phillips which shows a spring-biased, quick release locking assembly within the shaft, between a handle and blade of the paddle. The quick release locking assembly allows a user to pull the handle a short distance and rotate it so that a major axis of a grip member of the handle "may selectively be angularly aligned with and disaligned with a plane of the blade member". The blade may then enter the water at an angle offset to a plane perpendicular to a desired direction of travel. By pulling the offset blade toward the rear of the canoe, a counter turn pressure is generated tending to make the canoe move in a straight line. While the offset blade angle of Phillips solves some of the non-linear thrust problem of conventional paddles, it has not become popular for many reasons. First, the spring-biased quick release locking assembly is complicated, delicate, and exposed to extremely harsh, wet environments of outdoor water sports, and therefore has reliability problems. Second, to use the paddle on one side of the canoe and then on the other (as is done even if moving straight ahead to avoid asymmetric muscle use and fatigue, etc.) the user must pull the handle against spring pressure and re-set the angle of the grip member relative to the blade for opposed side usage, while traveling in the canoe, which is a challenge to comfortable balance, and also presents a risk of dropping the paddle. Third, while the offset angle of the blade to the grip member generates a counter turning force, that force is a result of the user's arms resisting a tendency of the paddle to slip into the canoe, toward the user. Resisting that slipping or lateral motion of the blade force requires a twisting or torsional force that must be applied by the user's wrists, which tires the wrists, especially during long, flat water passages.
Accordingly, known bent shaft paddles and off-set blade to grip member paddles have not solved common, well-known canoe paddle problems. Therefore it is a goal of the present ergonomic canoe paddle to provide a paddle that compensates for non-linear thrust, and that also enhances efficient blade movement through a full paddle stroke length.